Activated Carbon Filters Utilise a composite carbon material to remove gases and odours from the air.

AHU (Air Handling Unit) An item of plant within a ventilation system comprising a fan, heating and/or cooling coils and ductwork in which a filter(s) is located.

Air Flow The volume of air passing through the filter.

Air Filter A device designed to remove suspended particles from air flowing through it.

Arrestance A measure of the ability of a filter to remove a standardised test dust from the air passing through it under given operating conditions. Expressed as a weight percentage.

Bag/Pocket Filters An extended surface filter in which the medium is formed into pockets or bags which may be self-supporting or supported by the air flow through them.

Baffle Plate or vane used to direct or control movement of fluid or air within a confined area.

BS EN 779/ BS EN ISO 16890 Air Filters for General Ventilation

BS EN 1822 High Efficiency Air Filters

BSI British Standards Institution relating to the provision of standards across management systems, business improvements and regulatory approval.

Chemisorption Removal of gases from an airstream by the chemical reaction of gas with an impregnant on the surface of or distributed throughout the filter.

Compact Filters An extended surface filter in which the medium is pleated (typically into a 2 or 4 V-design) to create a larger filtration area in order to provide a high dust holding capacity.

Deep Pleat Media that has been folded into higher pleating formations using metal separators so that high dust holding capacities can be achieved.

DHC (Dust Holding Capacity) Amount of loading dust retained by the filter up to the final pressure drop.

Efficiency The ratio of the number of particles retained (by the filter) to the number entering it expressed in a percentage.

Electrostatic Filter Filtration system using electrically charged plates and an electrically charged thread that will give a charge to the passing particles so these will be attracted by the plates.

Eurovent Certification A pan European scheme that guarantees participating companies air filter performance to BS EN 779/16890, using a system of continuous monitoring and testing.

Face Velocity Air flow rate divided by the face area of a the filter expressed in meters/second.

FETA Federation of Environmental Trade Associations – UK body that represents the interests of manufacturers, suppliers, installers and contractors within the heat pump, controls, ventilating, refrigeration and air conditioning industry

Filter Area The effective area of media through which the air can pass.

Filter Class A term indicating a range of filter performance characteristics measured according to procedures in BS EN 779/BS EN ISO 16890 or BS EN 1822.

Filter Housings Dedicated units to secure the filter in place.

Final Pressure Drop The pressure drop up to which the filtration performance is measured for classification purposes. Also the point at which it is recommended to replace the filter.

Gasket A lip which runs around the front of the filter frame to ensure that no air (and its contaminants) escapes around the side of the filter within the AHU.

Glass Fibre Media A media made from glass fibre. Possesses low electrostatic charge and is subject to the danger of downstream filter fibre discharge, but has certain applications.

Grease Filters Filters typically used within kitchens to maintain hygiene standards. Also often a health and safety requirement, these filters collect grease and are usually available in permanent or washable formats.

HEPA (High Efficiency Particulate Air) A filter with an MPPS of between 85 - 99.995% and rated in the H- class by BS EN 1822. Also known as absolute filters.

HEVAC/HVAC Heating, Ventilation and Air Conditioning Manufacturers Association.

IAQ (Indoor Air Quality) The content of interior air.

ISO International Organisation for Standardisation

LEV Local Exhaust Ventilation.

Magnehelic Trade name for a diaphragm-activated gauge that measures resistance to air.

Media Pads and Rolls Filter media which is to be inserted into a filter frame. Typically supplied in either reel form or cut-to-size.

Mini Pleat Media that has been folded into smaller formations so it possesses excellent filtration characteristics.

MPPS (Most Penetrating Particle Size) The maximum particle diameter which will penetrate through the filter medium.

OEMs Original Equipment Manufacturers

Panel Filters Filters consisting of flat or pleated media packs surrounded by a frame (usually cardboard, plastic or metal).

Pleated/Pleats Filter media which is formed into homogenous shapes.

PPI Pores per Inch. A measurement of the porosity of foam materials.

Pre-filter Used in multi-stage applications to remove larger particles. Pre-filters often protect the more efficient filters found in the next stage and extend their life time.

Pressure drop - final Pressure drop up to which the filtration performance is measured for classification purposes.

Pressure drop - initial Pressure drop of the clean filter operating at its test air flow rate.

Safe Change System A filter housing that is sealed to allow the filters to be changed inside a protective system which eliminates the opportunity for any of the captured particles to be released into the surrounding environment. Particularly used in the filtration of harmful, toxic and radioactive substances in nuclear, biological and chemical applications.

Synthetic Media A media made from a polymer material. Used for is electrostatic characteristics and the vast array of differing materials available.

ULPA (Ultra Low Penetration Air) Filters with an efficiency greater then 99,9995 % for MPPS.